Backlight compensation for a computing device with two or more display devices

ABSTRACT

In some implementations, a computing device may include a first display device and a second display device. An embedded controller may determine a first amount of ambient light and a first current associated with the first display device and modify the first current to create a first modified amount of current associated with the first display device. The embedded controller may determine a second amount of ambient light and second current associated with the second display device. The embedded controller may determine a ratio of a first perceived brightness of the first display device to a second perceived brightness of the second display device and modify the second current until the ratio is within a predetermined amount from a target ratio.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to a computing device with two or moredisplay devices and, more particularly, to adjusting a backlight of atleast one of the two or more display devices to compensate fordifferences in brightness between the display devices caused by (a)manufacturing, (b) temperature, and (c) ambient lighting.

Description of the Related Art

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

For a computing device that has two (or more) display devices integratedinto the computing device, providing a user with an enjoyable userexperience may include providing a backlight brightness for both of thedisplay devices that is perceived by the user as being similar (e.g.,nearly identical). For example, the user may have an enjoyable userexperience if the user does not perceive one of the display devices asbeing significantly brighter than the other display device(s), e.g., theuser perceives all of the display devices as having a similarbrightness.

One issue related to providing a similar perceived brightness for two(or more) display devices is that, while a backlit panel of a displaydevice is capable of being manufactured to have a similar (e.g.,consistent) backlight across an individual panel, manufacturingtolerances may result in significant and perceivable brightnessdifferences between two or more panels. For example, brightness may varyup to 20% between display panels produced by the same manufacturingplant.

A second issue associated with providing a similar perceived brightnessfor two (or more) display devices is that, depending on the orientationof the computing device, the ambient light may vary between the twodisplay devices. For example, a particular display device may be in alocation that receives more ambient light than other display devices.The particular display device may appear less bright (e.g., washed out)compared to the other display devices.

A third issue associated with providing a similar perceived brightnessfor two (or more) display devices is that temperatures may vary amongthe display devices, thereby causing differences in brightness. Forexample, a tablet computing device with two display devices may locatethe motherboard behind a first display device and locate the batterybehind the second display device, causing the temperature of the twodisplay devices to vary during use. The brightness of each displaydevice may vary based in part on the temperature of each display device,causing differences in brightness.

SUMMARY OF THE INVENTION

This Summary provides a simplified form of concepts that are furtherdescribed below in the Detailed Description. This Summary is notintended to identify key or essential features and should therefore notbe used for determining or limiting the scope of the claimed subjectmatter.

In some implementations, a computing device may include a first displaydevice and a second display device. An embedded controller may determinea first amount of ambient light and a first current associated with thefirst display device and modify the first current to create a firstmodified amount of current associated with the first display device. Theembedded controller may determine a second amount of ambient light andsecond current associated with the second display device. The embeddedcontroller may determine a ratio of a first perceived brightness of thefirst display device to a second perceived brightness of the seconddisplay device and modify the second current until the ratio is within apredetermined amount from a target ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure may be obtainedby reference to the following Detailed Description when taken inconjunction with the accompanying Drawings. In the figures, theleft-most digit(s) of a reference number identifies the figure in whichthe reference number first appears. The same reference numbers indifferent figures indicate similar or identical items.

FIG. 1 is a block diagram of an architecture that includes a computingdevice with two display devices according to some embodiments.

FIG. 2 is a block diagram illustrating different orientations of adual-screen device according to some embodiments.

FIG. 3 is a block diagram illustrating modes of a dual-screen device ina vertical orientation according to some embodiments.

FIG. 4 is a block diagram illustrating modes of a dual-screen device ina horizontal orientation according to some embodiments.

FIG. 5 is a block diagram illustrating a dual-screen device in which theoperating system is in a clone mode according to some embodiments.

FIG. 6 is a block diagram illustrating a dual-screen device in which theoperating system is in a single display mode according to someembodiments.

FIG. 7 is a block diagram illustrating a dual-screen device in which theoperating system is in an extended display mode according to someembodiments.

FIG. 8 is a flowchart of a process that includes reading an ambientlight sensor (ALS) associated with a display device according to someembodiments.

FIG. 9 is a flowchart of a process that includes determining abrightness ratio of two display devices according to some embodiments.

FIG. 10 illustrates an example configuration of a computing device thatcan be used to implement the systems and techniques described herein.

DETAILED DESCRIPTION

For purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, calculate, determine, classify, process, transmit, receive,retrieve, originate, switch, store, display, communicate, manifest,detect, record, reproduce, handle, or utilize any form of information,intelligence, or data for business, scientific, control, or otherpurposes. For example, an information handling system may be a personalcomputer (e.g., desktop or laptop), tablet computer, mobile device(e.g., personal digital assistant (PDA) or smart phone), server (e.g.,blade server or rack server), a network storage device, or any othersuitable device and may vary in size, shape, performance, functionality,and price. The information handling system may include random accessmemory (RAM), one or more processing resources such as a centralprocessing unit (CPU) or hardware or software control logic, ROM, and/orother types of nonvolatile memory. Additional components of theinformation handling system may include one or more disk drives, one ormore network ports for communicating with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse,touchscreen and/or video display. The information handling system mayalso include one or more buses operable to transmit communicationsbetween the various hardware components.

The system and techniques described herein may automatically (e.g.,without human interaction) adjust the brightness of one or moresecondary (e.g., slave) display devices to match (e.g., within apredetermined amount) the brightness of a first (e.g., master) displaydevice. For example, a portable tablet computing device may include atleast two display devices, in which a first display device is attachedto a second display device that enables the first display device torotate between approximately zero and approximately three hundred andsixty degrees relative to the second display device. The hinge may befairly slim, thereby enabling the two display devices to be less thansix millimeters apart from each other. In some cases, a single organiclight emitting diode (OLED) panel may be folded to create the firstdisplay device and the second display device. Due to the close proximityof the two (or more) display devices to each other, adjusting thebrightness (e.g., perceived brightness) of the second display to closelymatch (e.g., approximate) the brightness of the first display mayprovide the user with a positive user experience when using the multipledisplay computing device. While a computing device with two displaydevices for illustration purposes, the techniques and systems may beapplied to a computing device with more than two display devices, e.g.,a computing device with a primary (master) display device and one ormore secondary (slave) display devices.

While the manufacturer of a display panel used in a display device maymatch and calibrate the brightness of the backlight of each displaydevices, manufacturing tolerances may enable significant (e.g.,perceivable) brightness variations between two or more display panels.For example, the brightness of two display panels manufactured at thesame location may vary by as much as between ten and twenty percent.Thus, asking the manufacturer to identify two (or more) display deviceswith approximately the same brightness may be time consuming, expensive,or both. Additionally, the amount of ambient light associated with eachdisplay device may vary based on the orientation and lighting conditionsin which the computing device us used. Furthermore, temperaturedifferences between the two (or more) display devices may causebrightness variations between the display devices. For example,different components may be located behind each of the display devicesand may cause temperature variations that result in differences inbrightness between the display devices.

The techniques and systems described herein may automatically adjust thebrightness of one or more secondary display devices to match (e.g.,within a predetermined amount) the brightness of a first display device.For example, each display device may have a set of one or moreassociated ambient light sensors (ALS), one or more brightnessmeasurement sensors, or both. Each set of ALS may measure an amount ofambient light associated with a corresponding display device. Eachdisplay device may include a circuit that measures an amount of currentbeing drawn (e.g., used) by one or more light emitting diodes (LEDs)used to provide a backlight to each display device. For example, in somecases, an amount of current used by all of the LEDs of the backlight ofeach display device may be measured. In other cases, an amount ofcurrent used by a portion of the LEDs of the backlight of each displaydevice may be measured. The amount of current used by the portion of theLEDs of the backlight of each display device may be extrapolated todetermine the total current draw for each display device. For example,if a display device has a 5×5 (“five by five”) LED backlight, e.g., fivestrings of five LEDs each, the current draw of one string of five LEDsmay be measured and multiplied by five to determine the total currentdraw of the LEDs associated with the display device.

The current draw and ambient light associated with the first displaydevice may be measured and the brightness of the first (e.g., master)display device adjusted to provide a particular (e.g., predetermined)brightness level. The current draw and ambient light associated witheach of the one or more secondary display devices may be measured. Aratio of the current draw of the master display device to the currentdraw of the secondary display device may be calculated. The ratio may becompared with a target ratio and the current associated with thesecondary display device may be repeatedly adjusted and the ratiore-calculated until the ratio of the current draw of the master displaydevice to the current draw of the secondary display device is within apredetermined amount of the target ratio.

For example, if the secondary display device is not as bright (e.g.,drawing less current, receiving more ambient light, at a highertemperature, or any combination thereof) as compared to the masterdisplay device, the amount of current being sent to the backlight LEDsof the secondary display device may be incrementally and repeatedlyincreased until the brightness of the secondary display device isapproximately the same as the brightness of the master display. Toillustrate, a duty cycle associated with a pulse width modulation (PWM)circuit that provides current to the backlight LEDs of the secondarydisplay device may be increased to increase a brightness of thesecondary display device.

If the secondary display device is brighter (e.g., drawing more current,receiving less ambient light, or at a lower temperature, or anycombination thereof) as compared to the master display device, theamount of current being sent to the backlight LEDs of the secondarydisplay device may be incrementally and repeatedly decreased until thebrightness of the secondary display device is approximately the same asthe brightness of the master display. For example, a duty cycleassociated with a PWM circuit that provides current to the backlightLEDs of the secondary display device may be decreased to decrease abrightness of the secondary display device.

Thus, the ambient light associated with a master display device and witha secondary display device may be determined. The current drawn by thebacklight LEDs of the secondary display device and the current drawn bythe backlight LEDs of the master display device may be determined. Aratio of the brightness of the master display device to the secondarydisplay device may be calculated. The brightness of the secondarydisplay device may be repeatedly and incrementally adjusted by adjustingan amount of current provided to the secondary display device until theratio is within a threshold amount of a target ratio. Thus, thebrightness of the secondary display device may be adjusted to be nearlythe same (e.g., within a predetermined amount of brightness) of themaster display device. In this way, the computing device mayautomatically compensate for manufacturing variations that causediffering brightness levels between the backlight of the secondarydisplay device and the backlight of the master display device. Further,the computing device may automatically compensate for perceiveddifferences in brightness between the secondary display device and themaster display device due to differences in ambient light between thetwo display devices. In addition, the computing device may automaticallycompensate for differences in brightness between the secondary displaydevice and the master display device due to changes in a temperature ofthe secondary display device and a temperature of the master displaydevice.

FIG. 1 is a block diagram of an architecture 100 that includes acomputing device with two display devices according to some embodiments.A computing device 102 may include a memory 104, a central processingunit (CPU) 106, and a graphics processing unit (GPU) 108. The GPU 108may be a separate device (e.g., integrated circuit) from the CPU 106 ormay be integrated into the CPU 106.

The computing device 102 may include at least a first display device 110and a second display device 112. The display devices 110, 112 may eachbe touch-sensitive display devices that are capable of receiving inputfrom a stylus or an appendage (e.g., finger).

An embedded controller 114 may monitor various parameters associatedwith the display devices 110, 112 and adjust a brightness of one of thedisplay devices 110, 112 such that the perceived brightness of thedisplay devices 110, 112 is approximately the same when the displaydevices are being viewed together. For example, one of the displaydevices, such as the first display device 110, may be configured as amaster display device and another of the display devices, such as thesecond display device 112, may be configured as a secondary displaydevice. Of course, in some cases, the first display device 110, may beconfigured as the secondary display device and the second display device112 may be configured as the master display device. The embeddedcontroller 114 may monitor parameters, such as current and ambientlight, associated with each of the display devices and compare abrightness of the secondary display device to the brightness of theprimary display device. The embedded controller 114 may adjust thebrightness of the secondary display device to appear approximately thesame as (e.g., within a predetermined amount of) the brightness of theprimary display device.

The first display device 110 may include a first set of backlight lightemitting diodes (LEDs) 116 and the second display device 112 may includea second set of backlight light emitting diodes (LEDs) 118. For example,if each of the display devices 110, 112 is approximately 4.5″×5.5″, eachset of backlight LEDs 116, 118 may include 5 strings of 5 LEDs=25 LEDs.Of course, the number of LEDs in each of the backlight LEDs 116, 118 mayvary (e.g., more than 25 or less than 25) depending on theimplementation.

The first display device 110 may include a first backlight driver 120 todrive (e.g., cause to illuminate) the backlight LEDS 116. The seconddisplay device 112 may include a second backlight driver 122 to drivethe backlight LEDS 118. A first current monitor 124 may monitor anamount of current being drawn (e.g., used) by at least a portion of thebacklight LEDs 116. In some cases, the first current monitor 124 maymonitor a portion of the backlight LEDs 116 and the amount of currentdraw that is measured may be extrapolated to determine the total currentdraw of the backlight LEDs 116. For example, if the backlight LEDs 116include 5 strings, with each string having 5 LEDs, the first currentmonitor 124 may measure the current draw of one string of 5 LEDs and themeasured current draw multiplied by 5 to determine the total currentdraw of the backlight LEDs 116. In other cases, the first currentmonitor 124 may monitor a current draw of all the backlight LEDs 116. Asecond current monitor 126 may monitor an amount of current being drawn(e.g., used) by one or more of the backlight LEDs 118.

The computing device 102 may include a first set (e.g., one or more) ofambient light sensors (ALS) 128 to measure ambient light associated withthe first display device 110 and a second set of ALS 130 to measureambient light associated with the second display device 112. The ALS128, 130 may include sensors that measure ambient light, sensors thatmeasure a brightness of the LEDs 116, 118, respectively, or both. Theembedded controller 114 may read first ALS data 132 that measures anamount of ambient light associated with the first display device 110 andmay read second ALS data 134 that measures an amount of ambient lightassociated with the second display device 112.

The embedded controller 114 may determine first current 136 from thefirst current monitor 124. The first current 136 may indicate an amountof current being used by at least a portion of the backlight LEDs 116.The embedded controller 114 may determine second current 138 from thesecond current monitor 126. The second current 138 may indicate anamount of current being used by at least a portion of the backlight LEDs118.

The embedded controller 114 may determine (1) the ALS data 132, 134 and(2) the current 136, 138. Based on this information, the embeddedcontroller 114 may determine whether (and by how much) to modify thebrightness of at least one of the display devices 110, 112. For example,if the ALS data 132 indicates that the first display device 110 is inbright sunlight (e.g., causing the first display device 110 to appearwashed out) and the ALS data 134 indicates that the second displaydevice 112 is in shade, the embedded controller 114 may adjust (e.g.,increase or decrease) a brightness of the first display device 110 byproviding a first instruction 140 to the first backlight driver 120 toadjust (e.g., increase or decrease) the brightness of the backlight LEDs116. The first instruction 140 may cause the first backlight driver 120to adjust a first pulse width modulation (PWM) 148 (e.g., adjusting aduty cycle of a square wave) associated with a current being supplied tothe backlight LEDs 116 by the first backlight driver 120. For example,the duty cycle of the PWM 148 may be increased to increase the amount ofcurrent being sent to the backlight LEDs 116 to increase a brightness ofthe backlight LEDs 116. As another example, the duty cycle of the PWM148 may be decreased to decrease the amount of current being sent to thebacklight LEDs 116 to decrease the brightness of the backlight LEDs 116.

The embedded controller 114 may determine the second ALS data 132 andthe second current 138 and determine a current ratio 144 of the secondcurrent 138 to the first current 136. The current ratio 144 may indicatea relative brightness of the second display device 112 to the firstdisplay device 110. The embedded controller 114 may compare the currentratio 144 to a target ratio 146. If the current ratio 144 differs fromthe target ratio 146 by more than a predetermined amount, the embeddedcontroller 114 may repeatedly (1) incrementally adjust (e.g., increaseor decrease) the brightness of the second display device 112, (2)measure the second current 138, (3) re-calculate the current ratio 144,and (4) compare the current ratio 144 to the target ratio 146, until thecurrent ratio 144 differs from the target ratio 146 by no more than thepredetermined amount.

To adjust the brightness of the second display device 112, the embeddedcontroller 114 may provide a second instruction 142 to the secondbacklight driver 122. For example, the second instruction 142 may causethe second backlight driver 122 to perform a PWM 150 that adjusts a dutycycle of a square wave supplying current to the backlight LEDs 118. Toillustrate, the duty cycle of the PWM 150 may be increased to increasethe amount of current being sent to the backlight LEDs 118 to increase abrightness of the backlight LEDs 118. The duty cycle of the PWM 150 maybe decreased to decrease the amount of current being sent to thebacklight LEDs 118 to decrease a brightness of the backlight LEDs 118.In some cases, the instructions 140, 142 may be sent via aninter-integrated circuit (I2C) or other similar bus.

Thus, the embedded controller 114 may adjust a brightness of the masterdisplay device and adjust a brightness of the secondary displaydevice(s) to match (e.g., within a predetermined amount) the brightnessof the master display. For example, the embedded controller 114 maydetermine the ALS data 132 and the first current 136. The embeddedcontroller 114 may determine whether to adjust the brightness of thebacklight LEDs 116. For example, if the ALS data 132 indicates that thefirst display device 110 is receiving a relatively small amount ofambient light (e.g., shade), the embedded controller 114 may increasethe brightness of the backlight LEDs 116 by sending the firstinstruction 140 to the first backlight driver 120 to increase the squarewave duty cycle of the first PWM 148. If the ALS data 132 indicates thatthe first display device 110 is receiving a relatively large amount ofambient light (e.g., bright sunlight or underneath a lamp), the embeddedcontroller 114 may decrease the brightness of the backlight LEDs 116 bysending the first instruction 140 to the first backlight driver 120 todecrease the square wave duty cycle of the first PWM 148.

After adjusting the first (e.g., master) display device 110, theembedded controller 114 may adjust the brightness of one (or more)secondary display devices, such as the representative secondary displaydevice 112, to match the brightness of the first display device 110. Forexample, the embedded controller 114 may determine the second ALS data134 from the second ambient light sensor(s) 130. The embedded controller114 may determine the second current 138 associated with the seconddisplay device 112. The embedded controller 114 may determine thecurrent ratio 144 of the first current 136 to the second current 138 andmay compare the current ratio 144 to the target ratio 146. In responseto determining that the current ratio 144 differs from the target ratio146 by more than a predetermined amount, the embedded controller 114 maysend the second instruction 142 to the second backlight driver 122 toadjust the second PWM 150 (e.g., by adjusting the duty cycle of a squarewave). For example, if the current ratio 144 (e.g., and based on thesecond ALS data 134) indicates that the backlight LEDs 118 may appearless bright than the backlight LEDs 116, the embedded controller 114 mayincrease the brightness of the backlight LEDs 118 by sending the secondinstruction 142 to the second backlight driver 122 to increase thesquare wave duty cycle of the second PWM 150. If the current ratio 144(e.g., and based on the second ALS data 134) indicates that thebacklight LEDs 118 may appear more bright than the backlight LEDs 116,the embedded controller 114 may decrease the brightness of the backlightLEDs 118 by sending the second instruction 142 to the second backlightdriver 122 to decrease the square wave duty cycle of the second PWM 150.The embedded controller 114 may determine the second current 138associated with the second display device 112, determine the currentratio 144 of the second current 138 to the first current 136, andcompare the current ratio 144 to the target ratio 146. If the currentratio 144 differs from the target ratio 146 by more than thepredetermined amount, the embedded controller 114 may send the secondinstruction 142 to the second backlight driver 122 to adjust the secondPWM 150 (e.g., by adjusting the duty cycle of a square wave). Thisprocess of measuring the second current 138, determining the currentratio 144 to the target ratio 146, and adjusting the second PWM 150 maybe repeated until the current ratio 144 differs from the target ratio146 by no more than (or less than) the predetermined amount, e.g.,indicating that the second display device 112 has a brightness that isapproximately the same brightness as the first display device 110. Thus,the brightness of the backlight LEDs 118 may be incrementally andrepeatedly adjusted until the brightness of the backlight LEDs 116, 118is perceived to be about the same, e.g., based on the ambient lightingassociated with the display devices 110, 112.

FIG. 2 is a block diagram 200 illustrating different orientations of adual-screen device (e.g., the computing device 102 of FIG. 1) accordingto some embodiments. The computing device 102 may include at least twodisplay devices 110, 112. The computing device 102 may be displayed in avertical (e.g., portrait) orientation 202 or a horizontal (e.g.,landscape) orientation 204. For example, in the vertical orientation202, the first display device 110 may be on one side (e.g., the leftside or the right side), the second display device 112 may be on anotherside (e.g., the right side or the left side), and a hinge 206 may jointhe first display device 110 to the second display device 112.Additional examples of the vertical orientation 202 are illustrated inFIG. 3. In the horizontal orientation 204, the first display device 110may be located at the top (or the bottom) of the computing device 102with the hinge 206 in the middle and the second display device 112 maybe located at the bottom (or the top) of the computing device 102.Additional examples of the horizontal orientation 204 are illustrated inFIG. 4.

FIG. 3 is a block diagram 300 illustrating additional verticalorientations of a dual-screen device according to some embodiments.Additional examples of the vertical orientation 202 may include a bookorientation 302 and a vertical tablet orientation 304. For example, in afirst book orientation 302(1), the first display device 110 may be onthe left and the second display device 112 may be on the right.Alternately, in a second book orientation 302(2), the second displaydevice 112 may be on the left and the first display device 110 may be onthe right.

In the vertical tablet orientation 304, the first display device 110 maybe on the left and the second display device 112 may be on the right. Ina first vertical tablet orientation 304(1), the first display device 110may be facing a user and the second display device 112 may be rotatedapproximately 360 degrees to face away from the user. In a secondvertical tablet orientation 304(2), the second display device 112 may befacing the user while the first display device 110 may rotatedapproximately 360 degrees to face away from the user.

FIG. 4 is a block diagram 400 illustrating additional horizontalorientations of a dual-screen device according to some embodiments.Additional examples of the horizontal orientation 204 may include a tentorientation 402, a presentation orientation 404, a horizontal tabletorientation 406, and a clamshell orientation 408.

In 402(1), the first display device 110 may be at the top facing theuser while the second display device 112 may be at the bottom facingaway from the user. In 402(2), the second display device 112 may be atthe top facing the user and the first display device 110 may be at thebottom facing away from the user.

In 404(1), the first display device 110 may be at the top facing theuser and the second display device 112 may be at the bottom facing down.In 404(2) the second display device 112 may be at the top facing theuser and the first display device 110 may be at the bottom facing down.

In 406(1), the first display device 110 may be at the top facing theuser and the second display device 112 may be at the bottom facing down(e.g., away from the user). In 406(2), the second display device 112 maybe at the top facing the user and the first display device 110 may be atthe bottom facing down (e.g., away from the user).

In 408(1), the first display device 110 may be at the top facing theuser and the second display device 112 may be at the bottom facing theuser (e.g., in a position where traditionally, a keyboard is located ina laptop). In 408(1), in some cases, a QWERTY-based keyboard may bedisplayed on the second display device 112 and used to receive keyboardinput. In 408(2), the second display device 112 may be at the top facingthe user and the first display device 110 may be at the bottom facingthe user (e.g., in a position where traditionally, a keyboard is locatedin a laptop). In 408(2), in some cases, a QWERTY-based keyboard may bedisplayed on the first display device 110 and used to receive keyboardinput.

FIG. 5 is a block diagram 500 illustrating a dual-screen device in whichthe operating system is in a clone mode according to some embodiments.An operating system of the computing device 102, such as Microsoft®Windows®, may provide three display modes: (a) an extended desktop modein which the display devices 110, 112 behave as if they were a singledisplay device, with the display device 112 behaving as an extension ofthe display device 110 (b) a clone mode in which each of the displaydevices 110, 112 display the same content, or (c) a single display mode,e.g., one of the display devices 110, 112 displays content while theother display device is off (or blank) and does not display content. Forexample, single display mode may be used when the computing device is ina tablet orientation to turn off a particular display device (of thedisplay devices 110, 112) that is not facing the user or not visible tothe user.

In the clone mode, first content 502 may be displayed on the firstdisplay device 110. The first content 502 may also be displayed on thesecond display device 112. Thus, the same content 502 may be displayedon both display devices 110, 112.

FIG. 6 is a block diagram 600 illustrating a dual-screen device in whichthe operating system is in a single display mode according to someembodiments. When an operating system of the computing device 102 ofFIG. 1 is in the single display mode, the first content 502 may bedisplayed on either (but not both) of the first display device 110 orthe second display device 112. For example, the first content 502 may bedisplayed on the first display device 110 and the second display device112 may not display any content (e.g., the second display device 112 maybe blank or off), as illustrated in the top of FIG. 6. As anotherexample, the first content 502 may be displayed on the second displaydevice 112 and the first display device 110 may not display any content(e.g., the second display device 112 may be blank or off), asillustrated in the bottom of FIG. 6.

FIG. 7 is a block diagram 700 illustrating a dual-screen device in whichthe operating system is in an extended display mode according to someembodiments. When the operating system of the computing device 102 ofFIG. 1 is in the extended display mode, some content, such as the firstcontent 502, may be displayed across both the first display device 110and the second display device 112. In some cases, additional content maybe displayed on either the first display device 110 or the seconddisplay device 112. For example, second content 702 may be displayed onthe first display device 110 and third content 704 may be displayed onthe second display device 112.

In the flow diagrams of FIGS. 8 and 9, each block represents one or moreoperations that can be implemented in hardware, software, or acombination thereof. In the context of software, the blocks representcomputer-executable instructions that, when executed by one or moreprocessors, cause the processors to perform the recited operations.Generally, computer-executable instructions include routines, programs,objects, modules, components, data structures, and the like that performparticular functions or implement particular abstract data types. Theorder in which the blocks are described is not intended to be construedas a limitation, and any number of the described operations can becombined in any order and/or in parallel to implement the processes. Fordiscussion purposes, the processes 800 and 900 are described withreference to FIG. 1, 2, 3, 4, 5, 6, or 7 as described above, althoughother models, frameworks, systems and environments may be used toimplement these processes.

FIG. 8 is a flowchart of a process 800 that includes reading an ambientlight sensor (ALS) associated with a display device according to someembodiments. The process 800 may be performed by one or more components,such as the embedded controller 114, of the computing device 102 of FIG.1.

At 802, master ALS data associated with a master display device may beread. At 804, secondary ALS data associated with a secondary display maybe read. For example, in FIG. 1, the embedded controller 114 may readthe first ALS data 132 from the first ambient light sensor 128associated with the first display device 110 and may read the second ALSdata 134 from the second ambient light sensor 130 associated with thesecond display device 112.

At 806, a master current associated with the master display device maybe measured. At 808, a secondary current associated with the secondarydisplay device may be measured. For example, in FIG. 1, the embeddedcontroller 114 may use the first current monitoring circuit 124 todetermine the first current 136 associated with the first display device110. The embedded controller 114 may use the second current monitoringcircuit 126 to determine the second current 138 associated with thesecond display device 112.

At 810, a brightness ratio identifying the brightness of the masterdisplay device relative to the brightness of the secondary displaydevice may be calculated. There are several different ways in which thismay be calculated. For example:Master_to_Slave_Ratio=(Current_(Master)×ALS_Adj_(Master))/(Current_(Slave)×ALS_Adj_(Slave))

-   Where:-   Master_to_Slave_Ratio=current ratio 144-   Current_(Master)=First Current 136,-   Current_(Slave)=Second Current 138,-   ALS_Adj_(Master)=an adjustment for ambient light based on first ALS    Data 132, and-   ALS_Adj_(Slave)=an adjustment for ambient light based on second ALS    Data 134.    The ALS_Adj (ALS adjustment) may take into account that current may    be higher when the ALS data for a display device is relatively high    (e.g., more current means a brighter backlight when there is a    greater amount of ambient light), and the current for a display    device may be lower when ALS data is relatively low (e.g., less    current means a dimmer backlight when there is a lower amount of    ambient light). For example, assume the current 136, 138 can range    (or can be scaled to range) between 0 and 100 milliamperes (mA), the    ALS data 132, 134 is measured and scaled to have a value between 0    (minimum ambient light, e.g., darkness) and 100 (maximum ambient    light, e.g., direct sunlight). Assume both display devices 110, 112    are set to the same brightness (e.g., without taking into account    ambient light), e.g., first current 136=50 mA=second current 138.    Assume that the computing device 102 is placed in the clamshell    orientation 408(1), with the first display 110 receiving more    ambient light than the second display 112, e.g., the ALS data 132=60    and ALS data 134=40. Assume the ALS adjustment=(100−ALS Data). The    embedded controller 114 may determine:    Master_to_slave_ratio=(50×(100−60))/(50×(100−40))=2000/3000=0.67    The above indicates that the first (e.g., master) display device 110    appears less bright than the second display device 112 because the    first display 110 is receiving more ambient light than the second    display 112. The embedded controller 114 may first adjust the first    display device 110 to account for the ambient light (e.g., the first    ALS data 132). For example, the embedded controller 114 may use a    formula to increase the first current 136 to achieve a target    brightness of the first display device 110 based on the ambient    light (the first ALS data 132), e.g., first current 136×(100−first    ALS data)>=N, where N=2800. Assume the embedded controller 114    increases the first current 136 from 50 to 70 to compensate for the    higher ambient light:    Master_to_slave_ratio=(70×(100−60))/(50×(100−40))=2800/3000=0.93

The embedded controller 114 may adjust the second PWM 150 until thebrightness of the backlight LEDs 118, under the corresponding ambientlight (e.g. as measured by the second ALS data 134), is within athreshold of the brightness of the backlight LEDs 116, under thecorresponding ambient light (e.g. as measured by the first ALS data132). For example, the embedded controller 114 may repeatedly decreasethe second current 138 from 50 to 47 (e.g., decrement by 1 from 50 to49, from 49 to 48, and from 48 to 47) to reach within a threshold of thetarget ratio 146:Master_to_slave_ratio=(70×(100−60))/(47×(100−40))=2800/2820=0.99Thus, the embedded controller 114 adjusts the current ratio 144 to bewithin 1% of the target ratio 146.

At 812, a determination may be made whether the brightness ratiosatisfies a target ratio. In response to determining, at 812, that “yes”the brightness ratio satisfies (e.g., is within a predetermined amountof) the target ratio, the process proceeds to 802, where the master ALSsensor data is read. For example, the embedded controller 114 maycalculate the current ratio 144 based on the ALS data 132, 134 and thecurrent 136, 138. The embedded controller 114 may compare the currentratio 144 to the target ratio 146 to determine if the perceivedbrightness (e.g., based on the ambient light) of the display devices110, 112 is approximately the same. The embedded controller 114 maydetermine whether the ratio of the master display brightness to thesecondary display brightness is within a predetermined amount (or withina predetermined percentage) of the target ratio 146. For example, if thetarget ratio is 1 (“one”) to achieve a perceived equal brightnessbetween the display devices 110, 112, the embedded controller 114 maydetermine whether the current ratio 144 (master_to_slave ratio) isbetween 0.98 and 1.02 to determine if the current ratio 144 is within0.02 (e.g., 2%) of the target ratio 146. The embedded controller 114 maydetermine whether the current ratio 144 (master_to_slave ratio) isbetween 0.95 and 1.05 to determine if the current ratio 144 is within0.05 (e.g., 5%) of the target ratio 146. If the computing deviceincludes more than two display devices, the ratio of the master displaydevice to each secondary display device may be determined and thecurrent of each secondary display device adjusted to match thebrightness of each secondary display device to the master displaydevice.

In response to determining, at 814, that “no” the brightness ratio doesnot satisfy (e.g., is not within a predetermined amount of) the targetratio, the process proceeds to 814, where the secondary currentassociated with the secondary display device is adjusted. The process800 then proceeds to 810 where the brightness ratio is re-calculated.The process 800 may repeat 810, 812, and 814 until, at 812, thebrightness ratio is determined to satisfy (e.g., is within apredetermined amount of) the target ratio. For example, if the currentratio is 1.10, indicating that the first display device 110 is about 10%brighter than the second display device 112, the embedded controller 114may repeatedly and incrementally (e.g., by 0.01) increase the second PWM150 to increase the second current 138 until the current ratio 144 is1.02 (e.g., within 2% of the target ratio 146) or 1.05 (e.g., within 5%of the target ratio 146). If the current ratio is 0.90, indicating thatthe first display device 110 is about 90% as bright as the seconddisplay device 112, the embedded controller 114 may repeatedly andincrementally (e.g., by 0.01) decrease the second PWM 150 to decreasethe second current 138 until the current ratio 144 is 0.98 (e.g., within2% of the target ratio 146) or 0.95 (e.g., within 5% of the target ratio146).

Thus, an embedded controller may determine the ambient light associatedwith a first (e.g., master) display device, determine a first currentbeing drawn (e.g., consumed) by the backlight LEDs of the first displaydevice, and adjust the first current to compensate for the ambientlight. For example, if the first display device is receiving more than apredetermined (“normal”) amount of ambient light, the embeddedcontroller may increase the amount of current being provided to thebacklight LEDs. If the first display device is receiving less than apredetermined (“normal”) amount of ambient light, the embeddedcontroller may decrease the amount of current being provided to thebacklight LEDs. For example, the current may be adjusted (e.g.,increased/decreased) by adjusting (e.g., increasing/decreasing) the dutycycle of a square wave (e.g., PWM) of a circuit providing power to thebacklight LEDs.

The embedded controller may determine the ambient light associated witha secondary display device, determine a second current being drawn bythe backlight LEDs of the second display device, and determine a currentratio of the perceived brightness of the first display device ascompared to the perceived brightness of the second display device. Theperceived brightness may be determined based on (1) the current beingdrawn by the backlight LEDs of each display device and (2) the ALS dataassociated with each display device. The current ratio may be comparedwith a target ratio. If the current ratio differs from the target ratioby more than a predetermined amount (or percentage), the embeddedcontroller may repeatedly and incrementally adjust the current beingsupplied to the backlight LEDs of the secondary display device andrecalculate the current ratio until the current ratio differs from thetarget ratio by no more than the predetermined amount (or percentage).

FIG. 9 is a flowchart of a process 900 that includes determining abrightness ratio of two display devices according to some embodiments.The process 900 may be performed by one or more components, such as theembedded controller 114, of the computing device 102 of FIG. 1.

At 902, data associated with a master display device may be read. At904, a brightness adjustment for the master display device may bedetermined. At 906, a brightness of the master display device may beadjusted. For example, in FIG. 1, the embedded controller 114 may readthe first ALS data 132 from the first ambient light sensor 128associated with the first display device 110 and may determine the firstcurrent 136 being drawn by the backlight LEDs 116 associated with thefirst display device 110. In some cases, the embedded controller 114 mayread one or more temperature sensors associated with the first displaydevice 110 to determine a temperature associated with the first displaydevice 110. For example, the display devices 110, 112 may use a type oftechnology that causes characteristics, such as brightness, of thedisplay devices 110, 112 to vary based on temperature. For example, heatbuild-up due to components (e.g., processor, memory, battery, or thelike) placed behind one or both of the display devices 110, 112 maycause one of the display devices to have a temperature that is differentfrom the other of the display devices. As another example, one of thedisplay devices 110, 112 may be in direct sunlight or below a heatregister, causing it to have an increased temperature as compared to theother of the display devices. In some cases, the temperature differencebetween the display devices 110, 112 may be sufficient to causedifferences in brightness. The embedded controller 114 may take thetemperature differences between the display devices 110, 112 intoconsideration when determining the current ratio 144 and when adjustingthe brightness of the second display device 112 to match the brightnessof the first display device 110. The embedded controller 114 may adjustthe brightness of the first display device 110 by adjusting the firstPWM 148 (e.g., adjusting a duty cycle of a square wave) based on thefirst ALS data 132 and the first current 136.

At 908, a master current associated with the master display device maybe measured and a secondary current associated with the secondarydisplay device may be measured. At 910, one or more master sensors(e.g., ALS sensors, temperature sensors, and the like) associated withthe master display device may be measured and one or more secondarysensors associated with the secondary display device may be measured.For example, in FIG. 1, the embedded controller 114 may use the firstcurrent monitoring circuit 124 to determine the first current 136associated with the first display device 110 and use the first ambientlight sensors 128 to determine the first ALS data 132. The embeddedcontroller 114 may use the second current monitoring circuit 126 todetermine the second current 138 associated with the second displaydevice 112 and use the second ambient light sensors 130 to determine thesecond ALS data 134. In some cases, the embedded controller 114 may readone or more master temperature sensors to determine a master temperatureassociated with the master display device and may read one or moresecondary temperature sensors to determine a secondary temperatureassociated with the secondary display device.

At 912, a brightness ratio comparing (1) the brightness of the masterdisplay device relative to (2) the brightness of the secondary displaydevice may be calculated. At 914, a determination may be made whetherthe brightness ratio satisfies a target ratio. The brightness ratio maybe calculated in different ways. In response to determining, at 914,that “yes” the brightness ratio satisfies the target ratio, the processproceeds to 902.

See the description of FIG. 8 for one example of how the brightnessratio may be determined. Another example of how the brightness ratio maybe determined and adjusted is described below.Master_to_Slave_Ratio=(Current_(Master)/ALS_Adj_(Master))/(Current_(Slave)/ALS_Adj_(Slave))

-   Where:-   Master_to_Slave_Ratio=current ratio 144-   Current_(Master)=First Current 136,-   Current_(Slave)=Second Current 138,-   ALS_Adj_(Master)=an adjustment for ambient light based on first ALS    Data 132, and-   ALS_Adj_(Slave)=an adjustment for ambient light based on second ALS    Data 134.    In some cases, (Current_(Master)/ALS_Adj_(Master)) may be multiplied    by a first temperature adjustment based on a first temperature of    the first display device and (Current_(Slave)/ALS_Adj_(Slave)) may    be multiplied by a second temperature adjustment based on a second    temperature of the second display device.

The ALS_Adj (ALS adjustment) may take into account that current may behigher when the ambient light (e.g., ALS data) for a display device isrelatively high (e.g., more current means a brighter backlight tocompensate for a greater amount of ambient light), and the current for adisplay device may be lower when ALS data is relatively low (e.g., lesscurrent means a dimmer backlight when there is a lower amount of ambientlight). For example, assume the current 136, 138 can range (or can bescaled to range) between 0 and 100 milliamperes (mA), the ALS data 132,134 is measured and scaled to have a value between 0 (minimum ambientlight, e.g., darkness) and 100 (maximum ambient light, e.g., directsunlight). Assume both display devices 110, 112 are set to the samebrightness (e.g., without taking into account ambient light), e.g.,first current 136=50 mA=second current 138. Assume that the computingdevice 102 is placed in the clamshell orientation 408(1), with the firstdisplay 110 receiving more ambient light than the second display 112,e.g., the ALS data 132=60 and ALS data 134=40. The embedded controller114 may determine:Master_to_slave_ratio=(50/60)/(50/40)=0.83/1.25=0.67The 50/60 ratio indicates that the first (e.g., master) display device110 appears less bright than the second display device 112 because thefirst display 110 is receiving more ambient light than the seconddisplay 112. The embedded controller 114 may first adjust the firstdisplay device 110 to account for the ambient light (e.g., the first ALSdata 132). For example, the embedded controller 114 may use a formula toincrease the first current 136 to achieve a target brightness of thefirst display device 110 based on the ambient light (the first ALS data132), e.g., first current 136/first ALS data 132>=N, where N=1. Assumethe embedded controller 114 increases the first current 136 from 50 to60 to compensate for the higher ambient light:Master_to_slave_ratio=(60/60)/(50/40)=1.0/1.25=0.80The embedded controller 114 may adjust the second PWM 150 until thebrightness of the backlight LEDs 118, under the corresponding ambientlight (e.g. as measured by the second ALS data 134), is within athreshold of the brightness of the backlight LEDs 116, under thecorresponding ambient light (e.g. as measured by the first ALS data132). For example, the embedded controller 114 may repeatedly decrementthe second current 138 from 50 to 40 to reach within a threshold of thetarget ratio 146:Master_to_slave_ratio=(60/60)/(40/40)=1.0Thus, the embedded controller 114 adjusts the current ratio 144 to bewithin a predetermined amount of (or equal to) the target ratio 146. Ofcourse, other techniques for determining and adjusting the ratio may beused. If the computing device includes more than two display devices,the ratio of the master display device to each secondary display devicemay be determined and the current of each secondary display deviceadjusted to match the brightness of the master display device.

In response to determining, at 914, that “no” the brightness ratio doesnot satisfy (e.g., is not within a predetermined amount of) the targetratio, the process proceeds to 916, where the brightness of thesecondary display device is adjusted. The process 800 then proceeds to918 where the secondary current associated with the secondary displaydevice is measured. The process 900 may repeat 912, 914, 916, 918 until,at 814, the brightness ratio is determined to satisfy (e.g., is within apredetermined amount of) the target ratio. For example, if the currentratio is 1.10, indicating that the first display device 110 is about 10%brighter than the second display device 112, the embedded controller 114may repeatedly and incrementally (e.g., by 0.01) increase the second PWM150 to increase the second current 138 until the current ratio 144 is1.02 (e.g., within 2% of the target ratio 146) or 1.05 (e.g., within 5%of the target ratio 146). If the current ratio is 0.90, indicating thatthe first display device 110 is about 90% as bright as the seconddisplay device 112, the embedded controller 114 may repeatedly andincrementally (e.g., by 0.01) decrease the second PWM 150 to decreasethe second current 138 until the current ratio 144 is 0.98 (e.g., within2% of the target ratio 146) or 0.95 (e.g., within 5% of the target ratio146).

Thus, an embedded controller may determine the ambient light associatedwith a first (e.g., master) display device, determine a first currentbeing drawn (e.g., consumed) by the backlight LEDs of the first displaydevice, and adjust the first current to compensate for the ambientlight. For example, if the first display device is receiving more than apredetermined (“normal”) amount of ambient light, the embeddedcontroller may increase the amount of current being provided to thebacklight LEDs. If the first display device is receiving less than apredetermined (“normal”) amount of ambient light, the embeddedcontroller may decrease the amount of current being provided to thebacklight LEDs. For example, the current may be adjusted (e.g.,increased/decreased) by adjusting (e.g., increasing/decreasing) the dutycycle of a square wave (e.g., PWM) of a circuit providing power to thebacklight LEDs.

The embedded controller may determine the ambient light associated witha secondary display device, determine a second current being drawn bythe backlight LEDs of the second display device, and determine a currentratio of the perceived brightness of the first display device ascompared to the perceived brightness of the second display device. Theperceived brightness may be determined based on (1) the current beingdrawn by the backlight LEDs of each display device and (2) the ALS dataassociated with each display device. The current ratio may be comparedwith a target ratio. If the current ratio differs from the target ratioby more than a predetermined amount (or percentage), the embeddedcontroller may repeatedly and incrementally adjust the current beingsupplied to the backlight LEDs of the secondary display device andrecalculate the current ratio until the current ratio differs from thetarget ratio by no more than the predetermined amount (or percentage).

FIG. 10 illustrates an example configuration of the computing device 102of FIGS. 1, 2, 3, 4, 5, 6, and 7 that can be used to implement thesystems and techniques described herein. The computing device 102 mayinclude one or more processors 1002 (e.g., the CPU 106 and the GPU 108of FIG. 1), memory 104, communication interfaces 1006, the displaydevices 110, 112, other input/output (I/O) devices 1010, and one or moremass storage devices 1012, configured to communicate with each other,such as via one or more system buses 1014 or other suitable connection.While a single bus 1014 is illustrated for ease of understanding, itshould be understood that the system buses 1014 may include multiplebuses, such as memory device buses, storage device buses, power buses,video signal buses, and the like.

The processors 1002 are one or more hardware devices that may include asingle processing unit or a number of processing units, all of which mayinclude single or multiple computing units or multiple cores. Theprocessors 1002 may include an integrated GPU or the GPU a separateprocessor device. The processors 1002 may be implemented as one or moremicroprocessors, microcomputers, microcontrollers, digital signalprocessors, central processing units, graphics processing units, statemachines, logic circuitries, and/or any devices that manipulate signalsbased on operational instructions. Among other capabilities, theprocessors 1002 may be configured to fetch and execute computer-readableinstructions stored in the memory 1004, mass storage devices 1012, orother computer-readable media.

Memory 1004 and mass storage devices 1012 are examples of non-transitorycomputer media (e.g., memory storage devices) for storing instructionsthat can be executed by the processors 1002 to perform the variousfunctions described herein. For example, memory 1004 may include bothvolatile memory and non-volatile memory (e.g., RAM, ROM, or the like)devices. Further, mass storage devices 1012 may include hard diskdrives, solid-state drives, removable media, including external andremovable drives, memory cards, flash memory, floppy disks, opticaldisks (e.g., CD, DVD), a storage array, a network attached storage, astorage area network, or the like. Both memory 1004 and mass storagedevices 1012 may be collectively referred to as memory or computerstorage media herein, and may be a media capable of storingcomputer-readable, processor-executable program instructions as computerprogram code that can be executed by the processor 1002 as a particularmachine configured for carrying out the operations and functionsdescribed in the implementations herein.

The computing device 102 may also include one or more communicationinterfaces 1006 for exchanging data via a network with other computingdevices. The communication interfaces 1006 can facilitate communicationswithin a wide variety of networks and protocol types, including wirednetworks (e.g., Ethernet, DOCSIS, DSL, Fiber, USB etc.) and wirelessnetworks (e.g., WLAN, GSM, CDMA, 802.11, Bluetooth, Wireless USB,cellular, satellite, etc.), the Internet and the like. Communicationinterfaces 1006 can also provide communication with external storage(not shown), such as in a storage array, network attached storage,storage area network, or the like. The display devices 110, 112 may beconnected to each other using a hinge (e.g., the hinge 206 of FIG. 2)that enables each of the display devices 110, 112 to rotate relative tothe other display device. The display devices 110, 112 may be used fordisplaying information and images to users. Other I/O devices 1010 maybe devices that receive various inputs from a user and provide variousoutputs to the user, and may include a stylus (e.g., to receive touchinput in the touchscreens of the display devices 110, 112, a keyboard, aremote controller, a mouse, a printer, audio input/output devices, andso forth. A controller 1018 may select a particular video signal routingconfiguration of a crossbar switch 1016. For example, the routings mayselect whether an output of an embedded DisplayPort (eDP) is sent to oneor both display devices 110, 112 and whether an output of a DisplayPort(DP) is sent to one or both display devices 110, 112. The computingdevice 102 may include one or more sensors 1020, such as, for example,temperature sensors associated with each of the display devices 110,112, the ambient light sensors 128, 130, an accelerometer, a gyroscope,a magnetometer or a magnetic compass, a proximity sensor, a camera, oranother type of sensor.

The computer storage media, such as memory 1004 and mass storage devices1012, may be used to store software and data. For example, the computerstorage media may be used to store temperatures 1022 (e.g., associatedwith each of the display devices 110, 112), an operating system 1024, adisplay mode 1026, an orientation module 1028 of the computing device102, one or more software applications 1030, and data 1032. Theoperating system 1022 may have the associated display mode 1026. Forexample, the operating system 132, such as Microsoft® Windows®, mayprovide three display modes 1026: (a) extended desktop mode where thedisplay devices 110, 112 behave as a single display device (e.g., thesecond display device 112 acts as an extension of the first displaydevice 110), (b) clone mode where each of the display devices 110, 112each display the same content, or (c) single display mode in which oneof the display devices 110, 112 is off or blank and therefore notdisplaying any content.

The example systems and computing devices described herein are merelyexamples suitable for some implementations and are not intended tosuggest any limitation as to the scope of use or functionality of theenvironments, architectures and frameworks that can implement theprocesses, components and features described herein. Thus,implementations herein are operational with numerous environments orarchitectures, and may be implemented in general purpose andspecial-purpose computing systems, or other devices having processingcapability. Generally, any of the functions described with reference tothe figures can be implemented using software, hardware (e.g., fixedlogic circuitry) or a combination of these implementations. The term“module,” “mechanism” or “component” as used herein generally representssoftware, hardware, or a combination of software and hardware that canbe configured to implement prescribed functions. For instance, in thecase of a software implementation, the term “module,” “mechanism” or“component” can represent program code (and/or declarative-typeinstructions) that performs specified tasks or operations when executedon a processing device or devices (e.g., CPUs or processors). Theprogram code can be stored in one or more computer-readable memorydevices or other computer storage devices. Thus, the processes,components and modules described herein may be implemented by a computerprogram product.

Furthermore, this disclosure provides various example implementations,as described and as illustrated in the drawings. However, thisdisclosure is not limited to the implementations described andillustrated herein, but can extend to other implementations, as would beknown or as would become known to those skilled in the art. Reference inthe specification to “one implementation,” “this implementation,” “theseimplementations” or “some implementations” means that a particularfeature, structure, or characteristic described is included in at leastone implementation, and the appearances of these phrases in variousplaces in the specification are not necessarily all referring to thesame implementation.

Although the present invention has been described in connection withseveral embodiments, the invention is not intended to be limited to thespecific forms set forth herein. On the contrary, it is intended tocover such alternatives, modifications, and equivalents as can bereasonably included within the scope of the invention as defined by theappended claims.

What is claimed is:
 1. A method comprising: determining, by a computingdevice comprising a first display device and a second display device, afirst amount of ambient light associated with the first display device;determining, by the computing device, a first current associated withthe first display device; determining, by the computing device, a secondamount of ambient light associated with the second display device;determining, by the computing device, a second current associated withthe second display device; determining, by the computing device, a firstperceived brightness associated with the first display device based onthe first current and the first amount of ambient light; determining, bythe computing device, a second perceived brightness associated with thesecond display device based on the second current and the second amountof ambient light; determining, by the computing device, a first ratio ofthe first perceived brightness of the first display device to the secondperceived brightness of the second display device; and modifying, by thecomputing device and based at least in part on the first ratio, thesecond current to create a second modified amount of current associatedwith the second display device, wherein the second modified amount ofcurrent modifies the second perceived brightness of the second displaydevice to create a modified second perceived brightness of the seconddisplay device.
 2. The method of claim 1, further comprising:determining a second ratio of the first perceived brightness of thefirst display device to the modified second perceived brightness of thesecond display device.
 3. The method of claim 2, further comprising:determining that the second ratio differs from a target ratio by lessthan a predetermined amount.
 4. The method of claim 2, furthercomprising: determining that the second ratio differs from a targetratio by at least a predetermined amount; and modifying the secondmodified amount of current to create a third modified amount of current.5. The method of claim 1, wherein modifying the second current to createthe second modified amount of current comprises: modifying a duty cycleof a square wave providing power to a backlight of the second displaydevice.
 6. The method of claim 1, wherein: increasing the second currentto create the second modified amount of current increases the modifiedsecond perceived brightness of the second display device.
 7. The methodof claim 1, wherein: decreasing the second current to create the secondmodified amount of current decreases the modified second perceivedbrightness of the second display device.
 8. A computing devicecomprising: a first display device; a second display device; an embeddedcontroller configured with logic instructions to perform operationscomprising: determining a first amount of ambient light associated withthe first display device; determining a first current associated withthe first display device; determining a second amount of ambient lightassociated with the second display device; determining a second currentassociated with the second display device; determining a first perceivedbrightness associated with the first display device based on the firstcurrent and the first amount of ambient light; determining a secondperceived brightness associated with the second display device based onthe second current and the second amount of ambient light; determining afirst ratio of the first perceived brightness of the first displaydevice to the second perceived brightness of the second display device;and modifying, based at least in part on the first ratio, the secondcurrent to create a second modified amount of current associated withthe second display device, wherein the second modified amount of currentmodifies the second perceived brightness of the second display device tocreate a modified second perceived brightness of the second displaydevice.
 9. The computing device of claim 8, further comprising: a firstambient light sensor to measure the first amount of ambient lightassociated with the first display device; and a second ambient lightsensor to measure the second amount of ambient light associated with thesecond display device.
 10. The computing device of claim 8, furthercomprising: a first backlight driver circuit to provide the firstcurrent to a first set of light emitting diodes (LEDs) associated withthe first display device; and a second backlight driver circuit toprovide the second current to a second set of light emitting diodes(LEDs) associated with the second display device.
 11. The computingdevice of claim 8, further comprising: a first set of temperaturesensors to determine a first temperature associated with the firstdisplay device; and a second set of temperature sensors to determine asecond temperature associated with the second display device.
 12. Thecomputing device of claim 11, the operations further comprising:determining the first ratio based at least in part on the firsttemperature and the second temperature.
 13. The computing device ofclaim 8, the operations further comprising: determining a second ratioof the first perceived brightness of the first display device to themodified second perceived brightness of the second display device;determining that the second ratio differs from a target ratio by atleast a predetermined amount; and modifying the second modified amountof current to create a third modified amount of current.
 14. One or morenon-transitory computer-readable storage media to store instructionsexecutable by a computing device to perform operations comprising:determining a first amount of ambient light associated with a firstdisplay device of the computing device; determining a first currentassociated with the first display device; determining a second amount ofambient light associated with a second display device of the computingdevice; determining a second current associated with the second displaydevice; determining a first perceived brightness associated with thefirst display device based on the first current and the first amount ofambient light; determining a second perceived brightness associated withthe second display device based on the second current and the secondamount of ambient light; determining a first ratio of the firstperceived brightness of the first display device to the second perceivedbrightness of the second display device; and modifying, based at leastin part on the first ratio, the second current to create a secondmodified amount of current associated with the second display device,wherein the second modified amount of current modifies the secondperceived brightness of the second display device to create a modifiedperceived brightness of the second display device.
 15. The one or morenon-transitory computer-readable storage media of claim 14 wherein: afirst backlight driver circuit provides the first current to a first setof light emitting diodes (LEDs) associated with the first displaydevice; and a second backlight driver circuit provides the secondcurrent to a second set of light emitting diodes (LEDs) associated withthe second display device.
 16. The one or more non-transitorycomputer-readable storage media of claim 14, the operations furthercomprising: determining a third current associated with a third displaydevice of the computing device; determining a third ratio of the firstperceived brightness of the first display device to a third perceivedbrightness of the third display device; and modifying the third currentto create a third modified amount of current.
 17. The one or morenon-transitory computer-readable storage media of claim 14, theoperations further comprising: determining a second ratio of the firstperceived brightness of the first display device to the second perceivedbrightness of the second display device; determining that the secondratio differs from a target ratio by at least a predetermined amount;and modifying the second modified amount of current to create a thirdmodified amount of current.
 18. The one or more non-transitorycomputer-readable storage media of claim 14, the operations furthercomprising: determining, using a first brightness sensor, a firstbrightness associated with the first display device; and determining,using a second brightness sensor, a second brightness associated withthe second display device.
 19. The one or more non-transitorycomputer-readable storage media of claim 14, the operations furthercomprising: determining an orientation of the computing device; anddetermining a display mode of the computing device.
 20. The one or morenon-transitory computer-readable storage media of claim 14, theoperations further comprising: sending an instruction to a backlightdriver associated with the second display device to create the secondmodified amount of current, wherein the instruction is sent via aninter-integrated circuit (I2C) bus.